This circuit disables the air conditioner compressor when additional engine power is required. It does so by monitoring the engine vacuum at the intake manifold. Ifthe vacuum drops to 40% of its normal level, the compressor clutch is disabled, removing the....

By using an RC oscillator and a programmable divider, this counter can run for hours. An interval osc..

The design delivers a regulated 400-V, 60-W output. The TL494 switching regulator governs the operating frequency and regulates output voltage. Rl and Cl determine switching frequency, which is approximately 0.SRC—100 kHz for the values shown. The TL494....

The microphone input, MIC1, is fed through C3 and R4 to inverting amplifier U2-a; the gain of U2-a is controlled by potentiometer R5. The output of U2-a is fed through C4 to the remaining op-amps (U2-b, U2-c, U2-d), which are all configured as....

The circuit can be used in telephone lines for speech activity detection purposes. This detection is very useful in the case of half-duplex conversation between two stations, in the case of simultaneous transmission of voice and data over the same pair of....

The detector will sense static charges and free ions in the air. It can be used to indicate the presence of ion emission, high voltage, static electricity, and electrostatic fields. The ground can be an earth ground or a touching metal by your hand...

Using two SCRs, this control circuit is designed to lock out the other SCR when one has been triggered, so only one lamp will light. Indicator lamp Il is controlled by SCRl. The operator simply presses switch Sl. Lamp I2 is similarly controlled by S2....

Transistor Q1-configured as a source-follower buffer stage, offering a bit under unity voltage gaingives tbe unit a high-impedance input of about 1 MO shunted by about 10 pF, which keeps only minimal loading on tbe equipment being tested. C1 serves as....

The circuit consists of a 5-V regulator, constant-current source Dl, D2, and Ql, and op amp gain stage Ul. Power is provid..

Half of a Motorola MG14538B dual, precision, retriggerable mono stable multivibrator is used to form an extended on-time timer circuit. That type of circuit can be used as a switch debouncer. Such circuits are often used in digital circuitry, where each and....

The Circuit shown can transmit voice to exceptionally good range. Tune trimmer to hear the signal to your near radio. Frequency range is 88-108 MHz. Max current consumption is 30mA. You can power the bug with a 9Volt Battery, or you can plug a power supply....

The circuit illustrates a method of interfacing a HEDS-1000 emitter-detector pair with a HA-5144 for use as a bar-code scanner circuit. The HA-5144 is used as an amplifier system which converts the bar and space widths of the printed bar code into a....

When the soil is moist, the LED glows. If the moisture falls below a certain predetermined level, the LED begins to flash. If there is still less moisture, the LED turns off. To calibrate, connect the battery and insert the probe into a container of dry....

This circuit shows a typical multiplex system intended to carry one of 8 inputs into a remote location. A 5-V pulse train is sent down a separate channel to perform timing and synchronizing functions. A 15-V reset pulse is superimposed on the 5-V clock,....

The circuit illustrates feedback speed regulation of a standard ac induction motor, a function difficult to accomplish other than with a costly, generator type, precision tachometer. When the apertured disc attached to the motor shaft allows the light beam....

The electronic gong is comprised of an oscillator (built around half of a 74COON quad 2-input NAND gate), an active twin-T filter (built around a TL081), and will drive an audio amplifier IC such as aii LM386N. Pulses from astable multivibrator ICl cause....

This circuit is a 555 timer IC connected as a square-wave generator. Its base frequency is approximately 45kHz, as detennined by the values of Rl, R2, and Cl. The 45-kHz carrier is frequency modulated by a modified trapizoidal voltage waveform applied to....

The purpose of D-type flip-flop IC2 is to synchronize the input signal with the clock pulse. When the clock pulse changes from low to high and the input is high, IC2 output is high. Subsequently, IC3 resets to zero and starts counting up. Until the counter....

When the ignition switch is on, relay K1 is energized continuously, and the headlights can be turned on. Turning off the ignition turns on timer IC1,which keeps IC1 energized for a time determined by Rl and CI. With the values shown approximately a 1 minute....

This electronic level uses two LED indicators instead of an air bubble. If the surface is tilted to the right, one LED lights; if it's tilted to the left, the other LED lights. When the surface is level, both LEDs light. It uses two unidirectional mercury....

When the touch plate is contacted by a large object (human body, etc.), stray 60-?? pickup is rectified by D1 and D2, and produces a negative voltage across R2-C2 and the gate of Q 1. Q1 cuts off, causes Q2 to conduct, and the output goes low. ..

This oscillator circuit includes a quartz crystal that has a nominal resonant frequency of 262,144 Hz and is cut in the orientation that gives a large linear coefficient of frequency variation with the temperature. In this type of circuit, the oscillation....

The piezo speaker, MICl, picks up the incoming ultrasonic signal and feeds it to the base of Ql. The two-transistor booster amplifier, Ql and Q2, raises the signal to a level that is sufficient to drive one input of this most unusual mixer circuit.....

This circuit operates like the one shown in Fig, 57-4, The only differences are that the field is placed across the rectified supply and the armature is placed in the SCR bridge. Thus the field current is unidirectionali)ut armature current is reversible;....

The car alarm here is a simple circuit with basic characteristics that cover all entrances at the car that has switches (doors etc).With one switch (arm-switch) the circuit waits for the sensor-switches to open and to activate it. So the horn with 1 sec....

Built around an Intersil 7216 frequency-counter IC, this counter has a basic range of 10 MHz, a 100-MHz prescaler, and an..

A JFET transistor-is used as a high-to-low impedance converter and signal mixer. Input impedance is approximately 50.0 kQ but it can be increased by increasing R5 to R8 as high as 10 . Output is about 2 kQ, but it can be increased or decreased by changing....

Power op amps provide accurate speed control for dc motors. The circuit provides bidirectional speed control. The amplifiers' push-pull configuration ensures a full rail-to-rail voltage swing (minus the output stages' saturation drops) across the motor in....

An inexpensive electronic thermometer is capable of measuring temperatures over a range of from -30°F to +120°F. A diode-connected 2N3904 transistor used as the temperature sensor forms a voltage divider with Rl. As temperature increases, the voltage drop....

The modified inverting amplifier uses an active clamp to limit the output swing with precision. Allowance must be made for the V8E of the transistors. The swing is limited by the base-emitter breakdown of the transistors. ..

The circuit uses two gates of a 7400 IC cross-connected to form an astable multivibrator driven by the 1-pulse per second output of the digital clock IC. The hee-haw circuit has a low frequency astable modulator added to make a self-contained European-type....

A pair of non-zenered MOSPOWER transistors, a pair of LEDs and a simple RC circuit make an easy sequential flasher with almost "unlimited sequencing time—from momentary to several seconds. The infinite input resistance of the MOSFET gate allows for very....